Leon wrote:

Ed Huntress wrote:
John Doe wrote:

Took it out in sunny afternoon 98°F weather for a 6 mile trip. The
20V 5AH battery shows one out of three bars remaining. Drill got hot
but there was no performance change.

This is really interesting, but I'm having trouble with some of the
numbers. Say the "two bars" consumption equals, roughly, 3 A-hr. At
20 volts, we have 60 W-hr. Just guessing here, but say you travelled
that 6 miles at 12 mph.

That means the drill was drawing an average of 120 W for a half-hour.
Let's be generous and say that the system efficiency is 80% from
storage to power at the drill shaft. So, given chain and friction
losses at the tire, you have 1/8 hp driving the bike.

Will that be enough to move you at 12 mph? I'm not familiar with the
actual power consumed by these bikes, but that sounds low. Am I
missing something?

Well consider also that the bars may not be an accurate indicator of
the state of charge.

For sure.

Since I didn't take the spare battery, as much as possible of the trip
was coasting. And I was trying to make sure the thing didn't overheat,
using full throttle (probably less than 12 mph) whenever possible so the
switch would bypass itself. The more powerful/capable drill will
probably be more fun and less worry in 98° late afternoon heat.

It was a strange trip using an unfamiliar mode of transportation.
Definitely not fast enough to be on the street when there is any traffic.
But the sidewalks are broken up and it's not a dirt bike. I hope to be
better prepared for rough terrain in the next planned version.

There are some cool possibilities to do with gearing. My next (planned)
drill low gear goes up to only 450 RPM. Some common freewheel cassettes go
up to 34 teeth. That probably means a 12 or 14 tooth front sprocket will
be powerful enough for the steepest hills around here (perhaps 15°, I
dunno). Keeping the rear sprockets, derailer, and shifter in place, it can
be quickly and easily shifted into a smaller/higher gear for greater
speed. Probably using no more than one or two other of the cogs, but it's
much quicker and easier than stopping to switch the drill speed range.